The drive to provide consumers with electronic, optoelectronic or any other components in a form that can be carried anywhere is driving the miniaturization of an ever wider array of technologies. From the cell phone to the solar cell, there exists a general need in the fabrication of microelectronic and optoelectronic devices for materials that can be deposited at low cost, are transparent, cured within a limited thermal budget and that can provide planarization of topography caused by complex device and interconnect structures.
Topography arises from processes that selectively add or remove materials in fabrication processes necessitating gap-fill and planarization requirements of dielectrics. New and emerging applications such as flexible displays use plastic substrates with severe topography (surface roughness) that also requires planarization or substrate smoothing as well.
Organic materials have limited application because of their high curing temperatures. For example, some novolac-based compositions including T27 ACCUFLO™, which is manufactured by Honeywell International Inc., require heating to temperatures as high as 275° C. in order to produce solvent resistant films. The use of those high temperatures causes competing reactions, such as oxidation, to occur that result in yellowing or darkening of the films, which is unacceptable for display applications.
Inorganic materials based on siloxanes are highly optically transparent; however, these inorganic materials crosslink only partially at temperatures below 300° C. and therefore contain residual silanol that can be detrimental to device characteristics. Outgassing, low electrical breakdown strength and high leakage result from residual silanols in siloxane-based films.
Therefore, it would be ideal to develop a family of low-temperature thermally curable polymer formulations that exhibit excellent planarization and gap fill, good thermal stability, low outgassing and excellent formulation shelf life, while at the same time, in some embodiments, minimizing yellowing or darkening of the resulting films. Methods of formulating these films, along with the specific chemistries, should be universal across organic and inorganic polymers.